Refa: only support MinerU-API now (#11977)

### What problem does this PR solve?

Only support MinerU-API now, still need to complete frontend for
pipeline to allow the configuration of MinerU options.

### Type of change

- [x] Refactoring

rag/flow/parser/parser.py

@@ -280,6 +280,7 @@ class Parser(ProcessBase):
                 binary=blob,
                 callback=self.callback,
                 parse_method=conf.get("mineru_parse_method", "raw"),
+                lang=conf.get("lang", "Chinese"),
             )
             bboxes = []
             for t, poss in lines: